As for the
nonsense on which many waste their labor and of which not even a
plausible account can be given, this we shall dismiss in favor
of
the primary natural causes.

-- Claudius Ptolemy, Tetrabiblos

Claudius Ptolemy's contribution to mathematics and astronomy was monumental,
one of the great scientific achievements of the ancient world.
His Almagest, written in the second century,
remained the standard work on astronomical theory and observation
until the time of Copernicus.

By contrast, Ptolemy's Tetrabiblos deals with the
pseudoscientific use of astronomy to make predictions about human affairs.

This site is under construction. Its purpose is:

to make available a translation into English of Ptolemy's "Tetrabiblos", and...

to explain this strange work in a way that I hope will gain sympathy from my fellow-scientists.

When the site is completed, I will argue that:

Ptolemy actually knew his system of divination really had no predictive value.

Ptolemy deliberately set up a system that allowed its practitioners
to reach pretty much whatever conclusions they wished.

The principal aim of the system was to help the government write propaganda.

Another purpose of the system was as props for lay counselling. This continues
to the present day and probably has real value.

Ptolemy also intended his work to help remove the shame and superstition connected with birth defects and the range
of interpersonal orientations.

Ptolemy's Tetrabiblos. The original
of the document is online at a Danish site, apparently scanned.
I have tried to correct the errors.